Method and device for evaluating the quality of a component produced by means of an additive laser sintering and/or laser melting method

ABSTRACT

A method for evaluating the quality of a component produced by means of an additive laser sintering and/or laser melting method, in particular a component for an aircraft engine, includes at least the steps of providing a first data set, which comprises spatially resolved color values, which each characterize the temperature of the component at an associated component location during the laser sintering and/or laser melting of the component, providing a second data set, which comprises spatially resolved color values corresponding to the first data set, which color values each characterize the temperature of a reference component at an associated reference component location during the laser sintering and/or laser melting of the reference component.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority from earlierfiled U.S. patent application Ser. No. 14/771,573, filed Aug. 31, 2015,which is a 371 national stage patent application of Patent CooperationTreaty International Application No. PCT/DE2014/000078, filed on Feb.27, 2014, and the entire contents thereof are incorporated herein byreference.

BACKGROUND OF THE INVENTION

The invention relates to a method for evaluating the quality of acomponent produced by means of an additive laser sintering and/or lasermelting method, in particular a component for an aircraft engine. Theinvention further relates to a device for carrying out a method of thistype.

Additive laser sintering and laser melting methods for the manufactureof components, such as, for example, components for aircraft engines,are already known as such from DE 10 2004 017 769 B4, for example. Inselective laser melting, thin layers of powder of the material ormaterials used are placed on a construction platform and locally meltedand solidified by using one or a plurality of laser beams. Theconstruction platform is then lowered and another layer of powder isapplied and again locally solidified. This cycle is repeated until thefinished component is obtained. The finished component can then befurther processed as needed or immediately used. In selective lasersintering, the component is produced in a similar way by laser-assistedsintering of powdered materials. However, laser sintering and meltingmethods have not been used so far for serial production of componentsfor aircraft engines. In addition, a process authorization, aprerequisite of which is the monitoring of diverse process parameters,such as, for example, the laser power as well as the nature and state ofthe powdered material and the like, is required, in particular, for theuse of components that are produced by additive laser methods and aresubject to high loads. In this case, the individual process parametershave to be monitored at intervals in the course of a process monitoringby means of a respectively adapted, elaborate method of measurement. Theinspection effort that thereby ensues is great and correspondinglytime-consuming and cost-intensive. Furthermore, a continuous monitoringof all relevant process parameters is often not possible a priori. Inaddition, all individual measurements must be harmonized with theirrespective tolerance ranges, as a result of which the analysis effort isadditionally relatively great in order to be able to make statementsabout the quality of the component produced by additive manufacturing.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to create a method for evaluatingthe quality of a component produced by means of an additive lasersintering and/or laser melting method, said method enabling an improvedevaluation of the quality of the produced component. Another object ofthe invention is to create a suitable device for carrying out such amethod.

The objects are achieved in accordance with the invention by a method aswell as by a device. Advantageous embodiments with appropriateenhancements of the invention are discussed in detail below, in whichadvantageous embodiments of the method are to be regarded asadvantageous embodiments of the device and vice versa.

A method according to the invention for evaluating the quality of acomponent produced by means of an additive laser sintering and/or lasermelting method comprises the steps of providing a first data set, whichcomprises spatially resolved color values, which each characterize thetemperature of the component at an associated component location duringthe laser sintering and/or laser melting of the component, providing asecond data set, which comprises spatially resolved color valuescorresponding to the first data set, said color values eachcharacterizing the temperature of a reference component at an associatedreference component location during the laser sintering and/or lasermelting of the reference component, determining a difference between thefirst data set and the second data set, and evaluating the quality ofthe component on the basis of the difference between the first data setand the second data set. In other words, it is provided in accordancewith the invention that a first data set is provided, which, for atleast certain positions of the component, includes a color value thatcharacterizes a temperature at this position during the manufacture ofthe component. The component and the reference component, which may alsobe referred to as the master part, can be, for example, a component foran aircraft engine. For quality evaluation, these color values (ortemperature values) are recorded in the course of a componentauthorization or acceptance based on a reference component and stored ina second data set, which is then provided for evaluating the quality ofan analogously produced component. All components that are subsequentlyproduced can thus be monitored simply and at will in real time bycomparing the color value distribution of the respectively producedcomponent to the corresponding color values of the master part for thecomponent coordinates considered. In this way, any differences betweenthe authorized reference component and the currently produced componentcan be determined and employed for evaluating the quality of thecomponent, thereby enabling an especially simple, rapid, andcost-effective quality evaluation of the laser-sintered component. Inaddition, by systematically recording fluctuations of typical processvariables, it is also possible to draw conclusions about all relevantprocess parameters and defects by means of only one comparison of data.The data sets can comprise, for example, data tuples of the form [x, y,z, color value], where x, y, and z are the component coordinates orglobal coordinates of a Cartesian coordinate system, for example. It isfundamentally possible also to be able to provide other suitable datastructures. When the first data set and the second data set exist indifferent data structures, a data transformation can be provided fordetermining any difference between the two data sets. It isfundamentally also possible to provide that the first and/or second dataset comprise or comprises additional measured values, metadata, etc.,besides color values of the component or of the reference component thatcharacterize the temperature. For example, the first and/or second dataset can additionally comprise color values that characterize thetemperature outside of the component, such as, for example, temperatureswithin a construction chamber in which the component is produced.

In an advantageous embodiment of the invention, it is provided that themethod is carried out one time or multiple times during the additivelaser sintering and/or laser melting of the component and/or for atleast one line element of the component and/or for at least one surfacearea element of the component and/or for at least one volume element ofthe component and/or for the entire component and/or subsequent to theadditive laser sintering and/or laser melting of the component. Bycarrying out the method at least one time during the manufacture of thecomponent, it is possible to detect directly any unallowed structuraldeviations from the reference component and, depending on the deviation,to correct them already during manufacture. If, already during themanufacture of the component, an unallowed and irreparable deviation isdetected, the finishing of the component can advantageously be dispensedwith, thereby avoiding unnecessary losses in time and material. Thedifference between the component and the reference component can bedetermined in this process fundamentally along a line element, that is,along a desired trajectory through the component, with respect to asurface area element, that is, with respect to a sectional plane throughthe component, and/or for a volume element of the component. Theanalysis can occur layer by layer during, for example, the buildup ofclass 2 or higher-class components for aircraft engines. In the case ofcomponents that are less critical to safety, one analysis over theentire component may also be sufficient.

In another advantageous embodiment of the invention, it is providedthat, on the basis of the determined difference, at least one otherparameter is determined from the group composed of powder consumption,powder condition, laser power, uniformity of powder deposition, layerthickness, travel path of a construction platform used for lasersintering and/or laser melting, strip overlap, irradiation parameters,transferability of the laser sintering and/or laser melting method to atype of laser sintering and/or laser melting equipment that differs fromthe type of laser sintering and/or laser melting equipment used for themanufacture of the reference component, aging phenomena of the lasersintering and/or laser melting equipment used, and machine drift of thelaser sintering and/or laser melting equipment used. In this way, it ispossible advantageously to determine further information relevant to themanufacture in the course of evaluating the quality of the componentand, as needed, to use this information to optimize the process.

In another advantageous embodiment of the invention, it is provided thatthe first data set and/or the second data set comprise(s) at least 1million and preferably at least 2 million spatially resolved colorvalues. In this way, especially reliable statements are made possiblestatistically. For example, the first data set and/or the second dataset can comprise 1.0 million, 1.5 million, 2.0 million, 2.5 million, 3.0million, 3.5 million, 4.0 million, 4.5 million, 5.0 million, 5.5million, 6.0 million, 6.5 million, 7.0 million, 7.5 million, 8.0million, 8.5 million, 9.0 million, 9.5 million, 10.0 million, or morespatially resolved color values.

Further advantages ensue when the first data set and/or the second dataset are/is created from measured values that are determined by using atleast one high-resolution detector and/or an optical thermographymethod. This permits an especially simple, precise, and cost-effectivedetermination of the energy input and a correspondingly simple, precise,and cost-effective creation of the respective data set. Moreover, it ispossible in this way to evaluate the quality of the component in anespecially precise manner, because, for example, nonuniformities in thematerial, in the layer thickness, or in the heat input can be determinedin an especially precise manner and can be stored in the form of acorresponding data set.

In another advantageous embodiment of the invention, it is provided thatgray-scale values are used as color values for the first data set and/orfor the second data set. In the context of the invention, gray-scalevalues refer to gradations between pure white and pure black. Becausegray-scale values represent brightness values, it is possible in thisway to achieve an especially simple and rapid analysis of thecorresponding data set and a corresponding simple and rapid evaluationof the quality of the component. Gray-scale values can be deposited inthe respective data set as values between 0 and 255, for example, or inhexadecimal notation, as values between #00 and #FF. It is fundamentallypossible also to provide coarser or finer gradations of the gray-scalevalue.

Further advantages ensue when the difference between the first data setand the second data set is determined by using at least one histogram ofthe component and at least one corresponding histogram of the referencecomponent and/or by using a cross correlation of the first and seconddata sets and/or by using an autocorrelation of the first data setand/or the second data set and/or by using a breakdown of the firstand/or second data set into harmonic components and/or by using adetermination of at least one line center of gravity and/or at least onesurface area center of gravity and/or a volume center of gravity of thecomponent and/or of the reference component. In this way, the method canbe adapted optimally to the respective circumstances and can be carriedout in a correspondingly rapid, simple, and precise manner. Moreover, asimple possibility is created in this way to perform a specific analysisof the component quality depending on whether different color orgray-scale values occur in large regions of one or a plurality ofsuccessive layers of the component or whether different color orgray-scale values occur in smaller regions or one or a plurality ofsuccessive layers of the component.

In another advantageous embodiment of the invention, it is provided thattoo low an energy input in the laser sintering and/or laser meltingprocess and/or a drop in laser power and/or a contamination of anoptical system of the laser sintering and/or laser melting equipmentare/is concluded when at least one color value at a component locationof the component is darker than a color value at a correspondingreference component location of the reference component. In this way, itis possible to make well-grounded inferences about possiblemanufacturing problems and method flaws, so that, by way ofcorresponding interventions in the laser sintering and/or laser meltingprocess, the proportion of defective components can be at leastsignificantly reduced or even completely prevented.

Accordingly, in a further advantageous embodiment of the invention, itis provided that too high an energy input in the laser sintering and/orlaser melting process and/or too high a laser power and/or a poor heatconduction in the sintered material powder and/or a wrong materialand/or a contaminated material and/or an aged material are/is concludedwhen at least one color value at a component location of the componentis brighter than a color value at a corresponding reference componentlocation of the reference component.

In another advantageous embodiment of the invention, it is provided thatthe component is classified as acceptable when the determined differencelies within predetermined limits or that the component is classified asnot acceptable when the determined difference exceeds the predeterminedlimits. In this way, it is possible in an especially simple manner todistinguish between acceptable or allowed components and defectivecomponents.

A second aspect of the invention relates to a device for carrying out amethod according to one of the preceding exemplary embodiments. Saiddevice according to the invention comprises at least one additive lasersintering and/or laser melting equipment unit for manufacturing acomponent, in particular a component for an aircraft engine, a detectiondevice, which is designed to record spatially resolved color values,which each characterize the temperature of the component at anassociated component location during laser sintering and/or lasermelting of the component, and a computing device. Said computing deviceis designed to generate a first data set from the spatially resolvedcolor values and to provide a second data set, with the second data setcomprising spatially resolved color values corresponding to the firstdata set, said color values each characterizing the temperature of areference component at an associated reference component location duringlaser sintering and/or laser melting of the reference component.Furthermore, the computing device is designed to determine anydifference between the first data set and the second data set and toevaluate at least the quality of the component on the basis of thedifference between the first data set and the second data set. In thisway, an especially rapid, simple, and detailed check and evaluation ofthe finished quality of the component is made possible. Further ensuingadvantages may be taken from the preceding descriptions of the firstaspect of the invention, whereby advantageous embodiments of the firstaspect of the invention are to be regarded as advantageous embodimentsof the second aspect of the invention and vice versa.

In an advantageous embodiment of the invention, it is provided that thedetection device comprises at least one high-resolution detector and/orat least one IR-sensitive detector, in particular a CMOS and/or sCMOSand/or CCD camera, for recording IR radiation. Detectors and cameras ofthe types of design mentioned are capable of replacing most availableCCD image sensors. In comparison to the previous generations ofCCD-based sensors and cameras, cameras based on CMOS and sCMOS sensorsoffer various advantages, such as, for example, a very low readoutnoise, a high image rate, a large dynamic range, a high quantumefficiency, a high resolution, and a large sensor area. After creationof the data set, this then enables an especially good quality inspectionof the manufactured component.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention ensue from the claims and theexemplary embodiments as well as on the basis of the drawings. Thefeatures and combinations of features mentioned above in the descriptionas well as the features and combinations of features mentioned below inthe exemplary embodiments can be used not only in the respectively givencombinations, but also in other combinations without departing from thescope of the invention.

Shown here are:

FIG. 1 a thermographic plan view of an additively manufactured layer ofa component, which has regions with different temperatures;

FIG. 2 a schematic plan view of a plurality of additively manufacturedcomponents with different temperature distributions;

FIG. 3 a schematic perspective view of a component, in which a qualityevaluation is carried out within a volume element;

FIG. 4 a histogram of a reference component;

FIG. 5 an overlap of a histogram of a component with a correspondinghistogram of the reference component;

FIG. 6 a schematically indicated cluster of histograms of the referencecomponent; and

FIG. 7 a schematic comparison between a histogram of the referencecomponent and an associated histogram of a component for evaluating thequality of the component.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a thermographic plan view of a layer of a component 10 foran aircraft engine, said component 10 being manufactured from acorresponding material powder by using an additive laser sintering orlaser welding method, which is known as such. On the one hand, alarge-area region 12, which has a uniform temperature distribution, and,on the other hand, a smaller region 14, which, in comparison to theregion 12, has a lower temperature, can be seen. The cross strips of theregion 12 symbolize, in addition, a direction of layering during theadditive manufacturing of the component 10. The temperatures arecharacterized in this case on the basis of spatially resolved gray-scalevalues, so that the region 14 appears darker than the region 12. Thetemperature values can be determined by thermographic methods andcompiled in a first data set for each measured component coordinate, forexample. In the process, the number of data points can be optimallyadjusted depending on the respective manufacturing method and/orcomponent.

The cause of the lower temperatures in the region 14 is primarily adeficient powder deposition. Too small a power deposition in the region14 leads to a correspondingly more rapid emission of heat and tocorrespondingly lower surface temperatures, which are characterized bylower gray-scale values. Further causes can be too low an energy inputin the region 14, owing to a drop in laser power, for example, acontamination of deflecting mirrors of the optical system, or the like.Vice versa, too high an energy input in the laser sintering and/or lasermelting process, too high a laser power, too poor a heat conduction inthe sintered material powder, an incorrect material, a contaminatedmaterial, and/or an aged material can be concluded when color orgray-scale values in one component region are markedly brighter than inother component regions.

FIG. 2 shows a schematic plan view of a plurality of jointly additivelymanufactured components 10 with different temperature distributions.Various brighter regions 12, which, correspondingly, have comparablyhigher temperatures, as well as various darker regions 14, which,correspondingly, have lower temperatures, can once again be seen. Thecause of the different temperature distribution in the present exampleis a flow of gas passing downward from above in the construction chamberof laser sintering equipment used for manufacturing the components 10,said flow of gas leading locally to a greater cooling effect and thus anaccumulation of comparatively colder component regions 14.

In order to be able to perform a reliable quality evaluation and, forexample, to make a reliable decision as to whether the regions 12 aretoo bright or the regions 14 are too dark, the first data set of thecomponent or components 10 is compared to a second, corresponding dataset of a reference component or a master part.

For this purpose, FIG. 3 schematically shows a perspective view of acomponent 10, which was additively manufactured on a constructionplatform 16. The quality evaluation of the component 10, which, forsimplicity, is depicted as being cube-shaped and has an edge length L,is carried out locally within a volume element 18 of the component 10.For this purpose, a first data set is provided, which comprisesspatially resolved color or gray-scale values, which each characterizethe temperature of the component 10 at an associated component locationwithin the volume element 18 during laser sintering. Furthermore, asecond data set is provided, which also comprises spatially resolvedcolor or gray-scale values, which each characterize the temperature of areference component within a corresponding volume element 18 duringlaser sintering and or laser melting of the reference component. Anevaluation of the quality of the component 10 can be performed bydetermining one or a plurality of differences between the first data setand the second data set.

FIG. 4 shows a histogram 20 of a reference component (not shown) in theviewed volume element 18, in which color or gray-scale values F areplotted on the ordinate axis and the corresponding spatial coordinate Lbetween the construction platform 16 and the top side of the component10 is plotted on the abscissa axis. The histogram 20 thus describes thetarget-value brightness or target-value temperature curve within thevolume element 18.

FIG. 5 shows an overlap of a histogram 22 of a component 10 in theviewed volume element 18 with a corresponding histogram 20 of thereference component. Various spatially dependent temperature deviationscan be seen. The differences in the spatially resolved temperaturevalues can be determined, for example, by using a comparison between thehistograms 20 and 22, by means of a cross correlation of the first andsecond data set of the volume element 18, by using an autocorrelation ofthe first data set and/or the second data set(s), by means of abreakdown of the first and/or the second data set(s) into harmoniccomponents, and/or by using a determination of a volume center ofgravity of the component 10 and of the reference component. If thedifferences exceed a predetermined limit value, the component 10 isclassified as being not acceptable. If, by contrast, the differences liewithin a predetermined tolerance range, the component 10 complies withthe reference component and thus with the predetermined specifications.

FIG. 6 shows a schematically indicated cluster of histograms 20 a to 20z along a corresponding cluster of lines La to Lz through the referencecomponent, which serve for global analysis of the component quality,that is, for evaluation of the entire component 10. As is clear fromFIG. 7, a comparison between each of the histograms 20 a to 20 z (here,histogram 20 f by way of example) of the reference component and anassociated histogram 22 a to 22 z (here, histogram 22 f by way ofexample) of the component 10 are taken for evaluation of the componentquality and, on the basis of any differences between the component 10and the master, it is decided whether the component 10 complies or doesnot comply with the required specifications.

The parameter values given in the documents for definition of processand measurement conditions for the characterization of specificproperties of the subject of the invention are to be regarded as alsobeing in the scope of the invention within the context of deviations—forexample, owing to measurement errors, system errors, weighing errors,DIN tolerances, and the like.

It would be appreciated by those skilled in the art that various changesand modifications can be made to the illustrated embodiments withoutdeparting from the spirit of the present invention. All suchmodifications and changes are intended to be covered by the appendedclaims.

What is claimed is:
 1. A method for evaluating the quality of acomponent produced by an additive laser sintering and/or laser meltingmethod, comprising the steps of: providing a first data set, whichcomprises spatially resolved color values, which each characterize thetemperature of the component at an associated component location duringthe laser sintering and/or laser melting of the component; providing asecond data set, which comprises spatially resolved color valuescorresponding to the first data set, said color values eachcharacterizing the temperature of a reference component at an associatedreference component location during the laser sintering and/or lasermelting of the reference component; determining a difference between thefirst data set and the second data set; and evaluating the quality ofthe component on the basis of the difference between the first data setand the second data set, wherein the difference between the first dataset and the second data sent is determined by: a comparison between atleast one histogram of the component and at least one correspondinghistogram of the reference component; and/or a cross correlation of thefirst and second data sets; and/or an autocorrelation of the first dataset and/or the second data set; and/or a breakdown of the first and/orthe second data set into harmonic components; and/or a determination ofat least one line center of gravity and/or at least one surface areacenter of gravity and/or a volume center of gravity of the componentand/or of the reference component.
 2. The method according to claim 1,wherein the method is carried out one time or multiple times duringadditive laser sintering and/or laser melting of the component and/orfor at least one line element of the component and/or for at least onesurface area element of the component and/or for at least one volumeelement of the component and/or for the entire component and/orsubsequent to the additive laser sintering and/or laser melting of thecomponent.
 3. The method according to claim 1, wherein, on the basis ofthe determined difference, at least one other parameter is determinedfrom the group composed of powder consumption, powder condition, laserpower, uniformity of powder deposition, layer thickness, travel path ofa construction platform used for laser sintering and/or laser melting,strip overlap, irradiation parameters, transferability of the lasersintering and/or laser melting method to a type of laser sinteringand/or laser melting equipment that differs from the type of lasersintering and/or laser melting equipment used for manufacture of thereference component, aging phenomena of the laser sintering and/or lasermelting equipment used, and machine drift of the laser sintering and/orlaser melting equipment used.
 4. The method according to claim 1,wherein the first data set and/or the second data set comprise/comprisesat least 1 million and preferably at least 2 million spatially resolvedcolor values.
 5. The method according to claim 1, wherein the first dataset and/or the second data set are/is created from measured values thatare determined by using a high-resolution detector and/or an opticalthermography method.
 6. The method according to claim 1, whereingray-scale values are used as color values for the first data set and/orfor the second data set.
 7. The method according to claim 1, wherein toolow an energy input in the laser sintering and/or laser melting processand/or a drop in laser power and/or a contamination of an optical systemof the laser sintering and/or laser melting equipment are/is concludedwhen at least one color value at a component location of the componentis darker than a color value at a corresponding reference componentlocation of the reference component.
 8. The method according to claim 1,wherein too high an energy input in the laser sintering and/or lasermelting process and/or too high a laser power and/or a poor heatconduction in the sintered material powder and/or an incorrect materialand/or a contaminated material and/or an aged material are/is concludedwhen at least one color value at a component location of the componentis brighter than a color value at a corresponding reference componentlocation of the reference component.
 9. The method according to claim 1,wherein the component is classified as being acceptable when thedetermined difference lies within predetermined limits, or in that thecomponent is classified as being not acceptable when the determineddifference exceeds the predetermined limits.
 10. The method according toclaim 1, further comprising the steps of: providing an additive lasersintering and/or laser melting equipment unit for manufacturing thecomponent, in particular a component for an aircraft engine; andproviding a detection device, which is designed to record the spatiallyresolved color values, which each characterize the temperature of thecomponent at an associated component location during laser sinteringand/or laser melting of the component.
 11. The method according to claim10, wherein the detection device comprises at least one high-resolutiondetector and/or at least one IR-sensitive detector, in particular a CMOSand/or sCMOS and/or CCD camera, for recording IR radiation.